The present invention relates generally to the field of fasteners, and more particularly to a "blind" rivet having a locking collar and a method for manufacturing such a rivet.
Blind rivets are specially designed to allow one or more workpieces to be fastened together without requiring access to the rear or blind side of the workpieces. Blind rivets have many industrial applications, and are also useful in the construction of aircraft. Typically, a blind rivet will be comprised of a tubular sleeve having a preformed head at one end. An elongated stem extends through the sleeve and terminates in an enlarged tail, which protrudes from the end of the sleeve opposite the preformed head.
To install such a blind rivet, the sleeve and stem are passed through a hole in the workpiece so that the preformed head abuts the front or accessible side of the workpiece, with the tail of the stem protruding through the rear side. An installation tool is used to pull on the end of the stem which protrudes through the preformed head while pushing against the preformed head, resulting in an equal force on the rivet. As a result, the tail of the stem is introduced to the sleeve. This causes the sleeve to expand radially and form a "blind head" on the rear side of the workpiece. The workpiece is thus sandwiched between the preformed head and the blind head.
Since the rivet installation is often subject to vibration, it is possible for the stem to come loose and slide back out of the sleeve even after the blind head is formed. To prevent this, previous blind rivets have provided a locking collar between the stem and the sleeve. The collar is deformed to expand radially and fill a lock groove surrounding the stem and a lock pocket within the preformed head. The lock pocket typically comprises a counterbore in the preformed head, of such a shape that the collar can be deformed into the counterbore by being compressed against a surface on the installation tool.
While previous locking collars have been satisfactory in terms of their ability to lock the stem in place, they have suffered from several drawbacks. The locking collar is most usually a separate part which must be formed independently of the sleeve and stem, and then wrapped around or assembled on the stem. Forming and installing the collar adds extra steps to the manufacturing process, in which large quantities of rivets must be produced economically, and to stringent quality standards.
In some previous designs, a locking collar has been formed as an integral part of the sleeve, and protrudes outwardly from the preformed head. During installation, the collar is separated from the head and driven into the sleeve. However, the method employed to form these integral locking collars has been complex and costly.
Further, previous locking collars have often required specially designed installation tools which engage the collar so as to cause its deformation, as discussed above. These installation tools are dedicated for use with a particular type and diameter fastener, and thus are unsuited for use with other types of fasteners or different diameter fasteners. As a result, a new set of installation tools must be purchased each time a rivet of a different type or diameter is to be used.
Thus, a need exists for a blind rivet with a locking collar that can be easily manufactured and installed with a variety of tools.